Future wireless communication and radar systems make use of complex signals with high Peak to Average Power Ratio (PAPR). High peak to average power ratio degrades efficiency performance of RF power amplifiers which results in power hungry transmitter design. On the other hand, high peak to average power ratio also dictates linear power amplification to maintain signal quality and spectral efficiency, which then compromise efficient use of power sources. RF outphasing transmitters lead the way to efficiently amplify amplitude varying wireless communication signals with switch mode RF power amplifiers.
Increasing demands in modern wireless communication systems, like high data rate and spectral efficiency lead to sophisticated and complex waveforms. These signal requirements are met with complex modulation schemes, which include amplitude, phase and frequency modulations, combined all together. Varying amplitude wireless communication signals require new transmitter architectures for an efficient and linear power amplification. Efficiency is needed to save energy sources and to use wireless devices for longer time; whereas linearity is essential to achieve high spectral efficiency and good signal quality.
In the known art, several transmitter architectures have been offered to amplify wireless communication signals. One of the known applications is Envelope Elimination and Restoration (EER) as disclosed in the Kim, Y. Y. Woo, S. Hong, B. Kim, “High efficiency hybrid EER transmitter for WCDMA application using optimized power amplifier”, in Proc. of 37th Eur. Microw. Conf. Dig., October 2007. However, envelope elimination and restoration transmitter requires a supply modulator to maintain high efficiency, which brings circuit complexity and shows limited efficiency performance for wideband signals.